1. Field of the Invention
This invention relates to medical prostheses for use in otologic surgery in the middle ear.
2. Description of the Prior Art
Heretofore, various stapedial prostheses have been developed. See, for example, Mercandino et al. (U.S. Pat. No. 3,191,188), Robinson (U.S. Pat. No. 3,196,462), Shea (U.S. Pat. No. 3,711,869) and Shakhov (U.S.S.R. Pat. No. 204,496). None of the above patents disclose or suggest the present invention.
In a healthy ear, the stapes extends from the lenticular process of the incus to the oval window for transmitting sound vibrations from the incus to the oval window. Due to various reasons, the stapes sometimes becomes defective and is replaced by a stapedial prosthesis. A major problem with all prior stapedial prostheses concerns the securing of the prosthesis to the incus. The Robinson prosthesis disclosed in U.S. Pat. No. 3,196,462 utilizes a wire loop for securing the prosthesis onto the incus. In this type prosthesis, there is the possibility of pressure necrosis (deadening or killing of bone cells) if the wire loop is applied too tightly and the possibility of dislocation of the prosthesis if the wire loop is applied too loosely. The Shea prosthesis disclosed in U.S. Pat. No. 3,711,869 overcomes the problem of pressure necrosis by having a socket provided in the head of the prosthesis which closely receives a portion of the lenticular process of the incus to secure the prosthesis to the incus. In this prosthesis, a loop extends from the head portion of the prosthesis and fits around the long process of the incus to insure that the prosthesis is held to the incus in the event that the portion of the lenticular process is dislodged from the socket. The loop does not normally contact the incus. In such a prosthesis there is the possibility of dislocation, resulting at best in inefficient transmission of sound vibrations from the incus to the oval window.